Ensure UKM only sends URLs under a specific length (currently 2K).

components/ukm/ukm_source.cc

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/ukm/ukm_source.h"
 
 #include "base/hash.h"
 #include "components/metrics/proto/ukm/source.pb.h"
 
 namespace ukm {
 
+namespace {
+
+// The maximum length of a URL we will record.
+constexpr int kMaxURLLength = 2 * 1024;
+
+// The string sent in place of a URL if the real URL was too long.
+constexpr char kMaxUrlLengthMessage[] = "URLTooLong";
+
+// Returns a URL that is under the length limit, by returning a constant
+// string when the URl is too long.
+std::string GetShortenedURL(const GURL& url) {
+  if (url.spec().length() > kMaxURLLength)
+    return kMaxUrlLengthMessage;
+  return url.spec();
+}
+
+}  // namespace
+
 UkmSource::UkmSource() = default;
 
 UkmSource::~UkmSource() = default;
 
 void UkmSource::UpdateUrl(const GURL& url) {
   DCHECK(!url_.is_empty());
   if (url_ == url)
     return;
   if (initial_url_.is_empty())
     initial_url_ = url_;
   url_ = url;
 }
 
 void UkmSource::PopulateProto(Source* proto_source) const {
   DCHECK(!proto_source->has_id());
   DCHECK(!proto_source->has_url());
   DCHECK(!proto_source->has_initial_url());
 
   proto_source->set_id(id_);
-  proto_source->set_url(url_.spec());
+  proto_source->set_url(GetShortenedURL(url_));
   if (!initial_url_.is_empty())
-    proto_source->set_initial_url(initial_url_.spec());
+    proto_source->set_initial_url(GetShortenedURL(initial_url_));
 }
 
 }  // namespace ukm